Lethal inhalation exposure during maintenance operation of a hydrogen fluoride liquefying tank.

Calcium sulfate adheres to the inside of liquefying pipes during the production of liquefied hydrogen fluoride. It is regularly washed away with water jets every six months. Two days before the operation, the pipes were experimentally washed down with water and the safety of the operation was confirmed with acidic washing fluid (pH 5). A 65-year-old man was severely sprayed on his face just after the start of the operation. He died half an hour later from acute respiratory failure. High serum concentrations of ionized fluoride indicated massive exposure to hydrofluoric acid (HFA). Pathological findings revealed severe bilateral pulmonary congestion and edema. It was hypothesized that calcium sulfate hardened with the water during the experimental washing and caused some blockages in the pipes. Consequently, choking of the pipes caused the HFA to collect and the washing fluid ran back. Weak HFA is not pungent to skin and mucous membranes. Therefore, it was suggested that a low concentration of HFA was inhaled directly into the peripheral respiratory tracts. No risk management against HFA exposure was in place during the operation. It is especially important to take thorough safety measures against inhalation of HFA. It is also essential that there are no stoppages of the pipes before the operation.